A device in which, in order to provide driving assistance for a vehicle, an obstacle located around the vehicle is detected by an ultrasonic sensor mounted on the vehicle has previously been proposed. According to such a device, abnormal operation of the ultrasonic sensor may cause a decrease in accuracy for detecting an obstacle. Thus, the device determines whether or not the ultrasonic sensor is operating normally.
For example, an obstacle detection device described in Patent Literature 1 determines that a permanent failure has occurred due to breaking of a wire or the like, when, after an oscillator of an ultrasonic sensor stops being driven, no reverberation signal is outputted from the oscillator. Furthermore, the obstacle detection device determines that a temporary failure has occurred due to freezing, contamination, or the like of the oscillator, when, after the oscillator stops being driven, a reverberation signal outputted from the oscillator is shorter than a normal time.